Laminate tubing prepared by coextrusion of polymer materials is known and used as catheter shafts or shaft segments and as parisons for preparation of catheter balloons.
In the manufacture of articles having multiple layers of polymers, it is known to include a tie layer between layers of immiscible polymers to improve adhesion. For instance in the manufacture of catheters and catheter balloons, a multilayer tube may be obtained by extrusion of different polymers. A first layer of high strength polymer such as polyester or polyamide, may be coextruded with a second layer, for instance of a polyolefin, fluorinated polymer, or ethylene acrylic acid copolymer, with an intermediate tie layer resin therebetween. Tie layers are sometimes formed of materials having some functional groups or chain fragments which have compatibility with the first layer material and other groups or chain fragments which have compatibility with the second layer material.
Patents which describe coextruded catheter tubing or balloon parison tubing, with or without tie layers, include U.S. Pat. No. 5,270,086 (Hamlin); U.S. Pat. No. 5,195,969 (Wang et al), U.S. Pat. No. 5,797,877 (Hamilton et al); U.S. Pat. No. 5,290,306 (Trotta); U.S. Pat. No. 5,478,320 (Trotta); U.S. Pat. No. 5,879,369 (Ishida); U.S. Pat. No. 6,319,228 (Kastenhofer); U.S. Pat. No. 6,464,683 (Samuelson et al). Materials which have been employed for tie layers include functionally modified polyolefins (for example, Plexar, available from Equistar Chemicals) or an adhesive resin such as Bynel from DuPont or Nucral (an ethylene methacrylic acid copolymer) available from DuPont.
Often tie layers formed of commercial thermoplastic materials are not entirely satisfactory. Sometimes the tie layer has insufficient similarity to one or the other of the layer materials. Commercial materials used for this purpose have not been tailored to the specific polymers employed in these applications and synthesis of a custom tie layer polymer, optimized to a specific combination of covering and underlying polymers, if possible, would require a skill level beyond that available to even very sophisticated device fabricators. It is therefore desirable to find improved tie layer materials and methods for preparation thereof which allow a fabricator to modify tie layer properties without engaging in substantial polymer synthesis activities.